Liquid transfer pipetting device with a tip ejector

ABSTRACT

A hand-held pipetter for extracting a predetermined volume of liquid from a body of liquid, including a movable piston within a piston chamber that is in fluid communication with a liquid receiving tip. A pair of cooperating cam lobes are provided so that relative rotation therebetween produces lateral motion of an ejector mechanism to force a used detachable tip off the pipetter without the necessity of touching the used tip by hand.

[ Nov. 11, 1975 ative produces lateral motion of an of touching the usedWITH A TIP EJECTOR Richard D. Reed, San Jose, Calif.

[73] Assignee: Oxford Laboratories Inc., Foster City, Calif.

May 30, 1973 Foreign Application Priority Data Apr. 16, 1973Germany............................ 23l9l75 73/425.6 B01L 3/02 Field73/425.6

References Cited UNITED STATES PATENTS l2/l974 S'cordato et UnitedStates Patent [54] LIQUID TRANSFER PIPETTING DEVICE [75] Inventor:

[22] Filed:

[21] App]. No.: 365,209

[51] Int.

US. Patent Nov. 11, 1975 LIQUID TRANSFER PIPETTING DEVICE WITH A TIPEJECTOR BACKGROUND OF THE INVENTION This invention is related generallyto hand-held liquid transfer devices, and, more specifically to suchdevices of a precision calibrated pipetting type. This application isrelated to an application of William J.- Roach entitled, Liquid TransferPipetting Device-with a Factory Adjustable and Sealable CalibrationStop.

Presently available hand-held liquid pipetting instruments are of a typeillustrated in US. Pat. No. 3,494,201 Roach (1970). Such devices includea tubelike barrel outer structure having a plunger extending outward ofone end thereof and a piston attached to the other end of the plungerand positioned within a piston chamber. The piston chamber is maintainedin fluid communication with an aperture at an end of the barrel handlewhich is shaped for frictionally engaging a detachable tip. The pistonis held in a normal rest position by one or more springs within thebarrel handle. When used to transfer liquid, the pipetter plunger isdepressed, the attached tip is placed in a liquid and the plungerreleased to draw a precise amount of liquid into the tip. The pipetteris then removed to a container for discharge of the liquid. The liquidis discharged from the tip by again depressing the plunger.

In order to make sure that all of the liquid is removed. from the tip,many available hand-held pipetting devices provide for moving theplunger (and thus the piston) an overshoot distance from the position towhich they were moved prior to drawing liquid into the tip. Such anovershoot feature prevents an error occurring in the volume of liquidtransfer, especially with liquids of high viscosity such as serum. Thepipetter of the aforementioned US. Pat. No. 3,494,201 accomplished suchovershoot by the use of two springs of significantly differingstrengths.

Another approach for providing the overshoot feature is described inco-pending patent application Ser. No. 282,321, filed Aug. 21, 1972. Inthis co-pending application, a single piston return spring is utilizedwithin the pipetting device while two spaced apart stops are provided onthe plunger for engaging the barrel end, the first stop to be used upondepressing the plunger prior to drawing liquid into a tip attachedthereto, and the second stop used upon discharge of the liquid from thetip with a piston overshoot distance. The two stops are selected bylateral movement of the plunger with respect to the pipetting barrelhandle as the plunger is depressed.

It is a primary object of the present invention to provide as part of ahand-held pipetter a mechanism for removing detachable tips therefromafter use and thereby to allow for such removal without an operatorhaving to touch a used tip. 1

It is another object of the present invention to provide an improvedinternal construction of a pipetter to permit a lateral movement of aplunger between positive stops thereof.

SUMMARY OF THE INVENTION These and additional objects are accomplishedby the various aspects of the present invention, one of which is theprovision of a cylindrical sleeve over a tube that is attached to apipetter barrel-like housing at one end and provided with means forengaging a hollow detachable plastic tip at its other end. Thecylindrical sleeve is resiliently held away from the tip holding end ofthe tube so as not to normally interfere with the engagement of a tipthereon. When a tip is desired to be removed, however, the sleeve ismanually actuated along the length of the tube to push a used plastictip off the end of the tube. Plastic tips are normally frictionallyengaged with the end of the tube but more positive means of latching mayalso be provided, the cylindrical sleeve having a capability of removingthat type of tip as well.

For the convenience of an operator, a pair of cooperating cam lobes areprovided, one attached to the pipetter barrel adjacent its tip holdingrod and the other attached to the sleeve. The spring normally holds thetwo lobes adjacent one another in a manner to provide space at the endof the tube for holding a detachable tip. When the lobe on the sleeve isrotated with respect to the barrel handle, however, that lobe rides upon the cam lobe of the barrel handle to convert the rotary motion tolongitudinal movement of the sleeve along the tube to dislodge the tipfrom the end of the tube.

The piston of the pipetter, according to another aspect of the presentinvention, terminates outside of the piston chamber in a disc whichextends across the width of the internal portion of the pipetter barrelhandle. A plunger extending through one end of the barrel handlecontacts the piston member end disc but is not integrally formedtherewith, thereby permitting lateral movement of the plunger forselecting a piston displacement volume without causing any such movementof the piston. A calibration stop is threadedly attached to the plungerinside the barrel handle. A spring normally urges the piston discagainst the plunger and the position of the callibration stops thereonthus determines how far the piston and the plunger will be forced by thespring toward said one end of the barrel handle. The calibration stopthereby determines the amount of fluid displaced in the piston duringone operation of the pipetter. The callibration stop is preferably acylindrical sleeve which is positioned to surround the plunger, thecylindrical sleeve having its end toward the piston disc closed andthreadedly attached to the plunger while the opposite open end of thecylindrical sleeve contacts an inside surface of the barrel handles saidone end for limiting travel thereof.

Additional objects, advantages and structural features of the variousaspects of the present invention will become apparent from the followingdetailed description of a preferred embodiment thereof which should betaken in conjunction with the accompanying drawmgs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates in a sectional viewa pipetter including the improvements of the various aspects of thepresent invention;

FIG. 2 shows a perspective view of the outside of a portion of thepipetter of FIG. 1; and

FIGS. 3 and 4 show in an enlarged view two parts of the pipetter ofFIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring primarily to FIG. 1,an upper portion 11 of a generally cylindrical elongated barrel handlemember has a lower portion 13 threadedly attached thereto. A finger hold15 is provided integrally with the upper barrel member 11. An elongatedtube 17 having a small bore 19 is rigidly attached to an extreme end ofthe lower barrel handle portion 13. A tip member 21 is provided at theextreme end of the tube 17 and rigidly attached thereto. The outsidesurface of the tip member 21 is conically shaped, in a very specificform, for frictionally engaging an internal surface of a conicallyshaped detachable tip 23. A bore 25 is provided through the tip member21 in order to provide fluid communication between the interior of thedetachable tip 23 and the bore 19.

At the opposite end of the barrel handle member is a plunger 27 having athreaded steel member 29 encapsulated in a plastic member 31. Theextreme plunger member 31 has a first stop surface 33 extending outwardtherefrom for limiting travel of the plunger assembly 27 into the barrelhandle by engaging an extreme outside surface 35 of an end of the barrelhandle member 1 l. A second stop surface 37 is provided for engaging thebarrel handle end surface 35 for depressing the plunger assembly 27 asecond further distance into the barrel handle 11. A knob, not shown, isattached to the extreme end of the plunger member 31 for receiving anoperators thumb when exerting force on the plunger assembly 27 to pushit into the barrel handle member 11. When so used, the fingers of theoperators hand are normally wrapped around the barrel member 11 underthe finger hold 15.

A piston chamber 39 is formed by a steel cylindrical sleeve 41 that isrigidly attached at one end thereof to the lower barrel handle member13. A cylindrically shaped solid piston member 43 has one end thereofpositioned within the piston chamber 39 through an end cap 45 attachedto the steel sleeve 41. A resilient O- ring 47 surrounds the piston 43for fluid sealing of that end of the piston chamber 39. The opposite endof the piston chamber 39 is provided in fluid communication with thebore 19 to result in fluid communication between the interior of adetachable tip 23 and the piston chamber 39.

The opposite end of the piston 43 is provided with a circular disc 49rigidly attached thereto and extending substantially entirely across thewidth of the interior portion of the barrel handle member 11. A spring51 is normally under compression to force the disc 49 and a movablemember 53 away from each other. The movable member 53 is slidable withinan aperture of a barrel member dividing piece 55 that is rigidlyattached to the barrel member 1 1 at its internal threads. The spring 51thus serves to hold the piston 43 at an extreme position with respect tothe piston chamber 39 and also to exert force through the slidablemember 53 against the resilient O-ring 47. A slot of the piston chamberend piece 45 in which the O-ring 47 is held is made to be smaller thanthe cross-sectional dimensions of the O- ring 47 so that the slidablemember 53 will push down upon the O-ring 47 rather than abuttingdirectly against the piston chamber end member 45. This force causes theO-ring 47 to expand against the piston 43 for improving the fluid sealtherebetween.

In order to provide a positive limited distance of travel of the piston43 out of the piston chamber 39, an adjustable calibration stop 57 isthreadedly attached to the plunger member 29. The adjustable stop 57, ina preferred form, is a cylindrical sleeve closed at the end thereof thatthreadedly engages the plunger member 29. An opposite end 59 of thecylindrical stop member 57 abuts against an inside surface of an end ofthe barrel handle member 11.

In use of the pipetting device shown in FIG. 1, the tip 23 has its freeend immersed in a liquid to be transferred to another container. Theplunger member 31 has been depressed until its stop surface 33 abuts thebarrel end surface 35. When the plunger 31 is permitted to return to itsrest position shown in FIG. 1 under the influence of the spring 51,liquid is drawn into the tip 23 as a result of the piston 43 withdrawinga distance from within the piston chamber 39. The pipetter is then movedso that the tip 23 is positioned over a container into which the liquidis to be transferred. The plunger 31 is then depressed to force theliquid out of the tip 23. For liquid discharge, it is generallypreferable to use the overshoot feature of the device by moving theplunger member 31 laterally with respect to the handle member 11 so thatthe stop surface 37 strikes the barrel end surface 35 rather than beinglimited in travel by the first stops surface 33.

The amount of liquid that is so transferred depends upon the distancethe piston 43 travels while liquid is drawn into the tip 23. This liquidvolume may be easily calibrated during the manufacture of each pipettingdevice by placing a calibrating block between the first stop surface 33and the barrel end surface 35. The plunger member 31 is then depressedto place this block under compression while the calibrating stop 57 isturned with respect to the plunger member 29 until its end 59 tightlyengages the inside surface of the barrel end. Some appropriate threadsealant, such as an epoxy resin, is applied to hold the calibration stop57 and the plunger member 29 firmly together to prevent relativerotation therebetween. Since force is exerted during use of the deviceon the engaging threads between the plunger member 29 and thecalibrating stop 57, these members are preferably made of a metal suchas stainless steel to prevent any change in the volume capability of thedevice through use and also for precision in the initial calibration.

It may also be noted that the force exerted on the O- ring 47 isincreased as the plunger assembly 27 is driven down into the barrelassembly 11 since such plunger action compresses the spring 51.Therefore, the drag on the piston 43 produced by frictional engagementwith the O-ring 47 is reduced as the piston 43 and plunger assembly 27are returned by the spring 51 to the rest position shown in FIG. 1. Thisassures a complete and smooth return of the piston 43 to its extremerest position and also reduces the wear on the O-ring 47 by reducing thefrictional drag thereon through at least a portion of the operatingcycle.

After a liquid sample has been transferred by the use of the pipettingdevice illustrated in FIG. 1, it is desirable to remove the detachabletip 23 without the operator having to touch it. Therefore, a mechanicaltip ejector is provided as part of the pipetter structure in order toreduce the possibility that contaminated liquid may be transferredthrough the hands of the operator from a used pipetter tip to some otherliquid or test apparatus. The tip ejector includes a hollowcylindrically shaped sleeve 61 positioned about the tube 17 with aspring 63 therebetween. An actuating member 65 is fixedly held to oneend of the ejecting sleeve 61. The spring 63 normally holds the actuator65 and the sleeve 61 as far against the lower barrel member 13 as itcan. In such a normal rest position, the sleeve 61 covers only a portionof the tip member 21, thereby leaving sufficient surface for positioninga detachable pipetter tip 23 thereon. The spring 63 pushes against asurface of the tip member 21 at one end and pushes against a surface ofthe actuator 65 at its other end.

The tip ejecting mechanism of the present invention may be operated bymoving the actuator 65 along the length of the tube 17 to push thedetachable pipette tip off of the pipetter end. For operatorconvenience, however, the cylindrical sleeve 61 and actuator 65 are alsomade to be rotable with respect to the tube 17. The basic pipetter andits ejecting mechanism are cooperatively designed so that such rotarymotion is converted into longitudinal motion for pushing a tip 23 offthe end of the pipetter. This is accomplished by providing cooperatingcam lobes 67 and 69. The cam lobe 67 is provided as an integral part ofthe actuator 65 on an internal surface thereof. A third cam lobe 71 isprovided on the actuator 65 and displaced 180 from its other cam lobe69. Only one cam lobe 67 is provided in this specific example, as partof the lower barrel handle member 13.

In the normal rest position of the tip ejector shown in FIG. 1, thelobes 69 and 71 of the tip actuator are positioned adjacent the lobe 67of the barrel handle member 13. When the actuator 65 is turned withrespect to the barrel handle member 13, however, one of the cam lobes 69or 71 of the actuator rides up onto the cam lobe 67, as shown in FIG. 2,thereby compressing the spring 63 and forcing the tip ejector sleeve 61against the tip 23. The cam lobes are preferably shaped at their tips sothat the position shown in FIG. 2 is an unstable one; that is, the lobes67 and 69 are shaped so that the force of the spring 63 will cause thelobes 67 and 69 to slip with respect to one another from the positionshown in FIG. 2 back to the rest position illustrated in FIG. 1.Additional cams could be used in order to reduce the amount of rotationthat is required to eject a tip but an increase in the number of camlobes either reduces the longitudinal travel possible of the tip ejectorsleeve 61 or makes the side slopes of the cam lobes so steep that therotatable force required to operate them is excessive. For smoothcontinuous action of the tip ejector, a low slope angle on the sides ofthe lobes 67, 69 and 71 is preferred.

Although the various aspects of the present invention have beendescribed with respect to a preferred embodiment, it will be understoodthat the invention is entitled to protection within the full scope ofthe appended claims.

I claim:

1. In a liquid transfer pipetting device that includes a hollow barrelshaped handle member, a piston chamber within said barrel, said pistonchamber having first and second ends, a piston element in said pistonchamber that extends through said first piston chamber end, meansextending through one end of said barrel member for imparting reciprocalmotion to said piston ele ment, resilient means within said barrel fornormally urging said piston element to a rest position toward said firstend of said piston chamber, and means extending from an opposite end ofsaid barrel for engaging a hollow detachable tip and for providing fluidcommunication between said second end of said piston chamber and aninternal portion of said tip, the improvement comprising mechanicalmeans associated with said tip holding means and responsive to manualactuation for disengaging a detachable tip from said tip holding means,said tip disengaging means includes a pair of cooperating cam lobes heldin a manner that rotation of an actuator with respect to said handlemember causes an ejecting means associated with said detachable tipengaging means to force a tip therefrom upon rotation of the actuator.

2. In a hand-held liquid transfer pipetting device that includes amanually actuated fluid pump within an enclosure member for providingfluid communication from said fluid pump to an end of said'tube memberre mote from the enclosure, said remote tube member end being shaped fora segment to frictionally engage an interior surface of a hollowdetachable tip, the improvement comprising:

a hollow sleeve held on said tube member in a manner to be rotatablewith respect thereto and also movable along its length from a firstposition wherein said tip engaging segment of the tube member remainsuncovered to a second sleeve position wherein at least a significantportion of said tip engaging segment of the tube member is covered,thereby permitting disengagement of a tip by breaking the frictionalbond therebetween as the sleeve is moved from its said first to its saidsecond position,

resilient means positioned for normally holding said hollow sleeve inits said first position, whereby a detachable tip is removed by movingsaid sleeve against the force of said resilient means, and

means cooperatively shaped between said tube member and said sleeve forconverting rotational motion therebetween into movement of the sleevealong said tube into said second sleeve position, whereby rotation ofsaid sleeve causes a tip to be ejected from frictional engagement withsaid remote tube member end.

3. The improved pipetter according to claim 2 which additionallycomprises a resilient means for normally holding said hollow sleeve inits said first position, whereby a detachable tip is removed by movingsaid sleeve against the force of said resilient means.

4. In a hand-held liquid transfer pipetting device that includes amanually actuated fluid pump within an enclosure member for providingfluid communication from said fluid pump to an end of said tube memberremote from the enclosure, said remote tube member end being shaped fora segment to frictionally engage an interior surface of a hollowdetachable tip, the improvement comprising:

a hollow sleeve held on said tube member and movable along its lengthfrom a first position wherein said tip engaging segment of the tubemember remains uncovered to a second sleeve position wherein at least asignificant portion of said tip engaging segment of the tube member iscovered, thereby permitting disengagement of a tip by breaking thefrictional bond therebetween as the sleeve is moved from its said firstto its said second position, resilient means for normally holding saidhollow sleeve in its said first position, whereby a detachable tip isremoved by moving said sleeve against the force of said resilient means,and first cam lobe attached to said enclosure member, a second matingcam lobe held fixed with respect to said sleeve and means for rotatingsaid cam lobes includes a manually actuated fluid pump within anenclosure member, and a hollow tube-like member extending from saidenclosure member for providing fluid communication from said pump to anend of said tube member remote from the enclosure, said remote tubemember end being shaped for holding an interior surface of a hollowdetachable tip, the improvement comprising:

a hollow cylindrical sleeve held on said tube in a manner to be movableboth longitudinally and ro- 5 tatably with respect to said tube member,

a coiled spring positioned within said sleeve and around the outside ofsaid tube member, said spring being attached in a manner to normallyurge said sleeve toward said enclosure member,

a first cam lobe attached as part of said enclosure member and extendingoutward adjacent said tube member, and

an actuator fixed to said sleeve at its end adjacent the enclosuremember, said actuator including a second cam lobe extending toward saidenclosure member for engaging said first cam when the actuator isrotated with respect to the to the enclosure member, thereby to providelateral movement of said sleeve along the tube member for disengagementof a tip frictionally held at a remote end of said tube member.

6. The improved pipetter according to claim 5 wherein said actuatorincludes a third cam lobe positioned from said second cam lobe, wherebythe actuator need be rotated a maximum of 180 to produce the desiredlaterla movement for removal of a detachable tip.

7. The improved pipetter of claim 5 wherein said actuator includes acylindrically shaped sleeve positioned to shield said first and secondcam lobes.

l= l= l l

1. In a liquid transfer pipetting device that includes a hollow barrelshaped handle member, a piston chamber within said barrel, said pistonchamber having first and second ends, a piston element in said pistonchamber that extends through said first piston chamber end, meansextending through one end of said barrel member for imparting reciprocalmotion to said piston element, resilient means within said barrel fornormally urging said piston element to a rest position toward said firstend of said piston chamber, and means extending from an opposite end ofsaid barrel for engaging a hollow detachable tip and for providing fluidcommunication between said second end of said piston chamber and aninternal portion of said tip, the improvement comprising mechanicalmeans associated with said tip holding means and responsive to manualactuation for disengaging a detachable tip from said tip holding means,said tip disengaging means includes a pair of cooperating cam lobes heldin a manner that rotation of an actuator with respect to said handlemember causes an ejecting means associated with said detachable tipengaging means to force a tip therefrom upon rotation of the actuator.2. In a hand-held liquid transfer pipetting device that includes amanually actuated fluid pump within an enclosure member for providingfluid communication from said fluid pump to an end of said tube memberremote from the enclosure, said remote tube member end being shaped fora segment to frictionally engage an interior surface of a hollowdetachable tip, the improvement comprising: a hollow sleeve held on saidtube member in a manner to be rotatable with respect thereto and alsomovable along its length from a first position wherein said tip engagingsegment of the tube member remains uncovered to a second sleeve positionwherein at least a significant portion of said tip engaging segment ofthe tube member is covered, thereby permitting disengagement of a tip bybreaking the frictional bond therebetween as the sleeve is moved fromits said first to its said second position, resilient means positionedfor normally holding said hollow sleeve in its said first position,whereby a detachable tip is removed by moving said sleeve against theforce of said resilient means, and means cooperatively shaped betweensaid tube member and said sleeve for converting rotational motiontherebetween into movement of the sleeve along said tube into saidsecond sleeve position, whereby rotation of said sleeve causes a tip tobe ejected from frictional engagement with said remote tube member end.3. The improved pipetter according to claim 2 which additionallycomprises a resilient means for normally holding said hollow sleeve inIts said first position, whereby a detachable tip is removed by movingsaid sleeve against the force of said resilient means.
 4. In a hand-heldliquid transfer pipetting device that includes a manually actuated fluidpump within an enclosure member for providing fluid communication fromsaid fluid pump to an end of said tube member remote from the enclosure,said remote tube member end being shaped for a segment to frictionallyengage an interior surface of a hollow detachable tip, the improvementcomprising: a hollow sleeve held on said tube member and movable alongits length from a first position wherein said tip engaging segment ofthe tube member remains uncovered to a second sleeve position wherein atleast a significant portion of said tip engaging segment of the tubemember is covered, thereby permitting disengagement of a tip by breakingthe frictional bond therebetween as the sleeve is moved from its saidfirst to its said second position, a resilient means for normallyholding said hollow sleeve in its said first position, whereby adetachable tip is removed by moving said sleeve against the force ofsaid resilient means, and a first cam lobe attached to said enclosuremember, a second mating cam lobe held fixed with respect to said sleeveand means for rotating said cam lobes with respect to one another,thereby providing movement of said sleeve between its said first andsecond positions in response to rotation of said lobe rotating means. 5.In a hand-held liquid transfer pipetting device that includes a manuallyactuated fluid pump within an enclosure member, and a hollow tube-likemember extending from said enclosure member for providing fluidcommunication from said pump to an end of said tube member remote fromthe enclosure, said remote tube member end being shaped for holding aninterior surface of a hollow detachable tip, the improvement comprising:a hollow cylindrical sleeve held on said tube in a manner to be movableboth longitudinally and rotatably with respect to said tube member, acoiled spring positioned within said sleeve and around the outside ofsaid tube member, said spring being attached in a manner to normallyurge said sleeve toward said enclosure member, a first cam lobe attachedas part of said enclosure member and extending outward adjacent saidtube member, and an actuator fixed to said sleeve at its end adjacentthe enclosure member, said actuator including a second cam lobeextending toward said enclosure member for engaging said first cam whenthe actuator is rotated with respect to the to the enclosure member,thereby to provide lateral movement of said sleeve along the tube memberfor disengagement of a tip frictionally held at a remote end of saidtube member.
 6. The improved pipetter according to claim 5 wherein saidactuator includes a third cam lobe positioned 180* from said second camlobe, whereby the actuator need be rotated a maximum of 180* to producethe desired laterla movement for removal of a detachable tip.
 7. Theimproved pipetter of claim 5 wherein said actuator includes acylindrically shaped sleeve positioned to shield said first and secondcam lobes.